show and hide div with element from code behind

Question

hi every body 

i want to switch between two divs on mouse over using code behind i try this but no way

how it can be done ???

this is my code

 

< div id = "myDiv" runat = "server" >

< p > triallllllll </ p >

</ div >

 

< div id = "myDiv2" runat = "server" >

< p > triallllllll </ p >

</ div >

 

 

in code behind by default 

myDiv.Style.Add("display", "");

 

how can i make mydiv hidden and mydiv2 is visible on mouse over ???

my page is inherted from masterpage